Overtravel switch actuator



April 1, 1947. N. QLFETTEIR" OVERTRAVEL SWITCH ACTUATOR Filed Feb. 5,1943 Patented Apr. 1, 1947 OVERTRAVEL swn'cn ACTUATOR Norman C. Fetter,Freeport, 1ll., assignor, by

mesne assignments, to First Industrial Corporation, Wilmington, Del., acorporation of Delaware Application February 5, 1943, Serial No. 474,804

' 6 Claims. 1 This invention relates to switches of the precisionsnap-acting type and has special reference to an improved actuatorconstruction for operating the switch mechanism.

.The principal objects of the invention are the provision of a switchactuator of short length' mounted directly in the switch housing andarranged to abut directly against the switch contact mechanism foroperating the same, the actuator comprising a tube having an end ofinsulation material bearing against the switch contact mechanism and thetube having support for axial movement in a relatively long bearingforming the mounting of the actuator and disposed in the housing of theswitch, the preferred embodiment comprising telescoping tubes in whichan overtravel spring is enclosed within the tubes and bearing againstthe insulated end so as to insulate the actuating mechanism from theswitch, both tubes having bearing support in said bearing, and one ofthe tubes carrying an adjusting means at its end for adjusting theeffective overall length of the actuator.

Other objects and advantages will be apparent from the followingdescription and the accompanying drawing, in which- Figure 1 is asection taken longitudinally through a switch mechanism embodying myinvention, and

Fig. 2 is a side elevation with a portion of the two switch housingsbroken away and showing the moved position of the switch contactmechanism and the switch actuator.

The actuator forming the subject matter of this invention is designedfor use with small precision snap-acting switches in which the size ofthe switch mechanism and housing isa matter of paramount importance.tended for use in confined space and under adverse'conditions where arelatively large amount These switches are in of current must beswitched and yet the dimensions of the switch must be maintained at aminimum and the parts must be protected from adverse surroundingconditions. These switches are designed for operation under a very smalldifferential of movement and under light operating pressures, and alsoare subject to damage.

if excessive forces are applied to the switch contact mechanism. Forthese reasons the form of the switch operating mechanism becomes amatter of paramount importance, and this invention deals primarily withan improved form of such operating mechanism. lhe invention is hereinshown as embodied in a switch mechanism of the type shown and describedin my copending application Serial No. 476,833 filed February 23, 1943now Patent No. 2,374,986, dated May 1, 1945, having a base 5 ofinsulating material and a cover 6 therefor, the base carrying astationary contact 1 adjacent one end and a supporting means 8 adjacentthe other end for supporting a switch contact mechanism, which in thisinstance comprises a spring Contact member 9 having two spaced tensionmembers ll, attached] at one end to the support 8 as shown, and acentral compression member l2, the opposite end of the compressionmember having pivotal support in an anchor it which in turn is pivotallymounted on a bracket 16 of the support 8. The compression. member isstamped integral with the tension members from a single piece'of springstrip. The tension and compression members, at their connected ends,carry an extension l3 upon which the mobile contact I4 is mounted. Aspring I! acts against the bottom of the anchor member 15 normallyurging it upward and thus bringing the contacts together in the mannershown in' Figure 1. When the anchor I5 is forced downward to theposition shown in Fig. 2, the contacts are caused to be separated toopen a circuit thereat. The base 5 and cover 6 form an inner insulatinghousing for the switch contact mechanism, and this inner housing isnormally enclosed in an outer housing l8 which is commonly formed ofmetal and has provision as shown at 19 for attachment to conduit orother means for enclosing electrical conductors.

The cover 6 has an opening 2| above the anchor i 5 and disposed in thisopening is a bearing member 22 which forms a bearing and a tubular guidefor the parts of the switch actuator. This bearing member has a boreprovided with a lower bearing surface 23 and an upper bearing surface 24separated by a shoulder 25. The outer surface of the bearing member hasa shoulder 26 adapted to abut against the outer surface of the innercasing and the lower end of the bearing member is riveted or spun overagainst the inner side of the inner housing as shown at 21 to retain thebearing rigidly in position on the inner housing. The bearing is ofsubstantially greater length. than the thickness of the inner housing soas to extend through an opening 28 in the outer housing and at the sametime to give greater length to the inner bearing surfaces. Positioned inthe lower end of the bearing portion and seated against the bearingsurface 23 is a tube 29 having an inwardly disposed shoulder 3| adjacentits upper end and near the shoulder 25 of the hearing member, theshoulder 3| being adapted to 3 abut the shoulder 25 to limit the upwardmovement of the tube. Disposed within the tube 29 is a second tube 32having an outwardly disposed shoulder portion 33 adapted to abut againstthe shoulder 3| for the purpose of limiting the relative extension ofthe two tubes, the shoulder portion.

33 being of substantial width slidable along the inner wall of the tube29 upon relative axial movement or the tubes in providing overtravelmovement to the actuator and to guide the lower end mechanism so as tooccupy a minimum of space from top to bottom. In this way the overall ofthe tube 32 against the inner wall of the tube 29 and thereby maintainalignment of th tubes throughout the length of travel or tube 32.Disposed across the lower end or the tube 29 is a button 34 having acrown portion 25 and an annular flange 36. The outer periphery of thejustments as between the actuator and the device from which the switchis operated. This flange 36 abuts againstthe shoulder 31 adjacent theend of the tube 29, and the outer end of the tube is riveted or spunover the outer surface of the flange 36 as shown at 38 to firmly retainthe button in place spanning the end oi the tube. The crown portion 35is adaptedto seat against the upper surface of the anchor member l5 soas to provide a substantially point contact as be tween the anchor andthe actuator.

The upper end of the tube 32 has a shoulder 39 and a centralthreaded/bore 4|, the bore 4i receiving in threaded engagement anadjusting screw 42 having a crowned head 48, a lock nut 44 beingdisposed on the screw tor the purpose of fixing the screw in adjustedposition on the tube. A compression spring 45 abuts at one end gainstthe shoulder 39 and at the other end against the insulating button 43.The button 43 has an upstanding central portion 49 which serves toprevent dislocation of the spring as is well known in the art. Thespring 45 and tube 32 are inserted in the outer tube 29 prior to theattachment of the button, and thereafter-the end of tube 29 is spun overthe annular flange 38 or the button so as to hold the tubes, the springand the button in assembled relationship.

It will be seen that the actuator is located in the housing in suchmanner that the crown 35 of the insulating button rests against ordirectly adjacent the upper surface of the anchor it when the anchor isurged upward against a stop screw 41 of the switch mechanism, and theshoulder 25 of the bearing member is in close proximity to the shoulder3! of the lower tube. Also motion can be transmitted from the upper tothe lower, tube through the spring 45. While the strength of this springcan be selected as desired, in this instance the spring is of suchstrength that the anchor is depressed before any substantial compressivemovement of the spring occurs. Thus,

-- when downward force is applied to the upper end However, when theanchor reaches the position shown in Fig. 2, continued downward movementof the adjusted screw'42 causes the upper tube 32 to telescope into thelower tube 29 and simultaneously compress the spring 39 in the mannershown in Fig. 2 allowing a substantial amount. of overtravel to occurwhich in the absence of the height of the switch mechanism and actuatoris maintained at a minimum and suflicient space is provided for theprovision oi the adjusting screw 42 for the purpose of making close adconstruction also provides substantially complete enclosure for thespring mechanism and permits manufacture and assembly of the actuator asa unit. Furthermore, the construction is such as to provide a relativelywide bearing for both tubes, which bearing is disposed both with-, inthe inner switch housing and above it in the area normally occupied bythe outer'housing l9. This reduces to a minimum any deviation inoperation due to side thrust o! the external operating member againstthe head of the adjusting pin 42.

1. The combination in an electric switch construction having a. housingand a switch contact mechanism therein of an overtravel'switch actuatorcomprising in combination two tubes disposed intelescoping assembly, oneof said tubes sliding within the other for extending and con-' tractingthe assembly, stops at one end of each of said tubes for limiting theextension of said assembly, a button of insulating material securedinthe other end oi! the largero! said tubes and adapted to bear againstsaid switch contact mechanism to operate the same, an internal shoulderat the other end of the smaller of said tubes, a coil compression springin said tubes bearing against said internal shoulder and against saidinsulating button to maintain said assembly in extended position, and abearing disposed in a wall of said housing for reciprocally Y supportingsaid assembly, said bearing having separate bearing surfaces to fit eachof said tubes for sliding movement of the assembly to actuate saidswitch contact mechanism.

2. The combination in an electric switch construction having a housingand a switch contact mechanism disposed therein, of an overtravelactuator comprising in combination a tubular bearing disposed in a wallof said housing and fixed thereto, two tubes supported in said bearingfor sliding axial reciprocating movement therein, one of said tubeshaving sliding engagement within the other for extending and contractingsaid tubes, stops at one end of each of said tubes for limiting theextension of said tubes; a button of electrical insulation secured inthe other end of one of said tubes and adapted to bear against saidswitch contact mechanism to operate the same, an internal'shoulder atthe other end of the other of said tubes, a spring in said tubes bearinagainst said internal shoulder and said insulating button and loaded-incompression to normally extend said tubes, and a threaded adjustablepush rod threaded into the other end of said other tube and extendinginto the coil'of said spring adapted to be screwed in and out of saidother'end for the purpose of other tube.

changing the extent ofits projection from said 3. The combination in anelectric switch conof said tubes, a button of electrical insulationsecured in the other end of one of said tubes and adapted to bearagainst said switch contact mechanism to operate the same, an internalshoulder at the other end of the other of said tubes, and a spring insaid tubes bearing against said internal shoulder and said insulatingbutton and loaded in compression to normally extend said tubes,saidspring having a strength sufficient to transmit the force requiredto actuate said switch contact mechanism without substantial distortionand to permit compression of the spring thereafter to provide overtravelmovement in said actuator.

4. The combination in an electric switch construction having a switchcontact mechanism and an enclosing housing therefor, of an overtravelactuator comprising a telescoping plunger including an outer tube havingan internal shoulder at one end providing a stop and an inner tubularpart telescoping therein, the tubular part having an enlarged annularshoulder on the outer surface thereof adjacent one end adapted to abutagainst said stop to limit the degree of extension of said plunger andto bear in sliding engagement against the inner surface of said tube tomaintain said tubes in axial alignment, a spring within said tube andsaid tubular part for extending said plunger, means carried on the endof said tube for supporting the thrust of said spring and for bearingagainst said switch contact mechanism to actuate the same in responsetoaxial movement of said plunger, said means comprising an insulatingbutton afllxed in the end of the tube and spanning the bore thereof forelectrically insulating said actuator from said switch mechanism ands.threaded adjustable push rod threaded into the other end of saidtubularpart adapted to be screwed in and out of said part for thepurpose of changing the extent of its projection to change the effectivelength of the overtravel mechanism.

5. The combination in an electric switch construction having a switchcontact mechanism and a housing for enclosing the same. of an overtravelactuator comprising abearing member mounted in a wall of said housingand extending therethrough, said bearing member having coaxial upper andlower bearing surfaces, the lower bearing surface being of greaterdimensions to provide a transverse shoulder therebetween, two tubescomprising an outer and an inner tube disposed in telescoping assemblymounted in said bearing member, said outer tube being disposed insliding and guiding relationship with said lower bearing surface andengageable with said shoulder to limit the movement of the assemblyoutwardly 5 and said inner tube being mounted in sliding and guidingrelationship with said upper bearing surface. a bearingv shoulder on theouter side of said inner tube at one end thereof slidable along theinner wall of said outer tube upon telescoping In movement of said tubesto maintain said tubes in axial alignment, 9. button of insulatingmaterial secured in one end of said outer tube adapted to bear againstsaid switch mechanism'to operate the same, an internal shoulder at theother endof said inner tube, and a coiled compression spring in saidtubes bearing against said internal shoulder and against said button tomaintain said tubes in extended position.

6. The combination in an electric switch construction having a switchcontact mechanism and a housing for enclosing the same, of an overtravelactuator comprising a bearing member bearing surface and engageable withsaid shoulder to limit the movement of the assembly outwardly and saidinner tube being mounted in sliding and guiding relationship with saidupper 7 bearing surface, an annular stop on the inner side of said outertube at one end thereof, a bearing shoulder on the outer side of saidinner tube at one end thereof for abutment against said stop to limitthe extended position of said tubes. said bearing shoulder beingslidable along the inner wall of said outer tube upon telescopingmovement of said tubes to maintain the tubes in axial alignment, abutton of insulating material se- 5 cured in one end of said outer tubeadapted to bear against said switch mechanism to operate the same. aninternal shoulder at the other end of said inner tube. and a coiledcompression spring in said tubes bearing against said internal shoulderand against said button to maintain said tubes in extended position.

' NORMAN 0. Emma.

nnrnnauons crran 55 The following references areof record the the ofthis patent:

. UNITED STATES PATM'I'B Number Name Date 2,181,068 Riche -4..- Nov. 21,1939 2,239,031 Bierenfeld et al. Apr. 22, 1941 2,071,149v Wilms et al.Feb. 16, 193'! 2,328,874 Meuer Aug. 17, 1943 2,174,868

Coffeen pet. a. 1939,

